Multiple lumen heat exchange catheters

ABSTRACT

Catheter devices and methods for intravascular heating and/or cooling of human or veterinary patients. The catheter devices generally comprise catheters having inflow and outflow lumens and at least one curvilinear balloon connected to the inflow and outflow lumens such that heat exchange fluid may be circulated through the balloon(s). The catheter is inserted into the vasculature and heated or cooled fluid is circulated through the balloon(s) to heat or cool blood flowing in heat-exchange proximity to the balloon(s), thereby effecting heating or cooling of all or a portion of the patient&#39;s body.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/855,521 filed and issuing on Jan. 19, 2016 as U.S. Pat. No.9,237,964, which is a continuation of U.S. patent application Ser. No.12/511,015 filed Jul. 28, 2009 and issued Apr. 2, 2013 as U.S. Pat. No.8,409,265, which is a continuation of U.S. patent application Ser. No.10/442,483 filed May 21, 2003 and issued on Jul. 28, 2009 as U.S. Pat.No. 7,566,341, which is a continuation of U.S. patent application Ser.No. 09/777,612 filed Feb. 6, 2001 and issued on Aug. 26, 2003 as U.S.Pat. No. 6,610,083, which claims priority to previously filedProvisional Application Ser. No. 60/181,249 filed Sep. 2, 2000 and whichis also a continuation-in-part of a) U.S. patent application Ser. No.09/138,830 filed Aug. 24, 1998 and issued on Sep. 16, 2003 as U.S. Pat.No. 6,620,188 and b) U.S. patent application Ser. No. 09/489,142 filedJan. 21, 2000 and issued on Aug. 6, 2002 as U.S. Pat. No. 6,428,563, theentire disclosure of each such related patent and application beinghereby expressly incorporated herein by reference.

This invention relates generally to medical devices and a method ofusing them for selectively affecting the temperature of a patient'sbody, or portion of the patient's body, by adding or removing heat fromthe patient's body fluid through the use of a heat exchange catheterwith a heat exchange region in contact with the body fluid, the heatexchange region being shaped for maximum heat exchange with minimuminsertion profile and minimum obstruction to the flow of the body fluid.More particularly, this invention relates to a heat exchange catheterwith a heat exchange region which is an advantageously shaped balloon,wherein the balloon is placed in flowing body fluid and heat exchangefluid circulates within the balloon to add or remove heat from the bodyfluid in order to treat or induce whole body or regional hypothermia orhyperthermia. This invention also relates to a method of controlling theamount of heat removed or added by the heat exchange region to affectthe temperature of all or part of the patient's body in response to asignal representing the temperature of all or part of a patient's body.

BACKGROUND OF THE INVENTION

Under ordinary circumstances, thermoregulatory mechanisms exist in thehealthy human body to maintain the body at a constant temperature ofabout 37° C. (98.6° F.), a condition sometimes referred to asnormothermia. Normothermia is generally a desirable condition, and tomaintain normothermia, the thermoregulatory mechanisms act so that heatlost to the environment is replaced by the same amount of heat generatedby metabolic activity in the body.

For various reasons, a person may develop a body temperature that isbelow normothermia, a condition known as hypothermia, or a temperaturethat is above normothermia, a condition known as hyperthermia. Theseconditions are generally harmful and are usually treated to reverse thecondition and return the patient to normothermia. In certain othersituations, however, they may be desirable and may even be intentionallyinduced.

Accidental hypothermia may result when heat loss to the environmentexceeds the body's ability to produce heat internally or when a person'sthermoregulatory ability has been lessened due to injury, illness oranesthesia. For example, a person exposed to a cold environment such asa hiker wandering in a very cold climate for too long, or a sailoroverboard in cold water, may become dangerously hypothermic. Likewise,anesthesia generally disables a patient's thermoregulatory ability, andit is often the case that, during long surgery with significant exposureof the patient's internal body cavities, a patient becomes significantlyhypothermic. Such hypothermia is generally harmful, and must be quicklyreversed to restore the victim to health.

Simple methods for treating hypothermia have been known since very earlytimes. Such methods include wrapping the patient in blankets,administering warm fluids by mouth, and immersing the patient in a warmwater bath. If the hypothermia is not too severe, and the need toreverse the hypothermia is not to urgent, these methods may beeffective. However, wrapping a patient in a blanket depends on theability of the patient's own body to generate heat to re-warm the body.Administering warm fluids by mouth relies on the patient's ability toswallow, and is limited both in the temperature of the liquid consumedand the amount of fluid that may be administered in a limited period oftime. Immersing a patient in warm water is often impractical,particularly if the patient is simultaneously undergoing surgery or someother medical procedure

More recently, hypothermia may be treated by the application of awarming blanket that applies heat to the skin of the patient. Applyingheat to the patient's skin, however, may be ineffective in providingheat to the core of the patient's body. Heat applied to the skin has totransmit through the skin by conduction or radiation which may be slowand inefficient, especially if the patient has a significant layer offat between the warming blanket and the body's core.

Paradoxically, if the patient is suffering significant core hypothermia,the application of warmth to the patient's skin, whether by immersion inhot water or application of a warm blanket, may actually exacerbate thecore hypothermia and may even induce shock. The body's thermoregulatoryresponses to cold that work to conserve heat in the body's core includevasoconstriction and arterio-venous shunting (AV shunts).Vasoconstriction occurs when the capillaries and other blood vessels inthe skin and extremities constrict so that most of the blood pumped bythe heart circulates within the core rather than through the skin andextremities. Similarly, in AV shunting, naturally occurring blood shuntsexist between some arteries providing blood to capillary beds in theskin and extremities and veins returning blood from those capillary bedsand extremities. When the body is cooled, the vessels in the capillarybeds constrict, and the shunts may be opened, causing blood to by-passthose capillary beds altogether. Thus when the body is cold, the tissuesin the extremities, and particularly at the surface, have little bloodflowing to them and may become quite cold relative to the body's coretemperature.

When heat is applied to the skin of such a patient, the temperaturesensors in the skin may cause the vasoconstriction to reverse and the AVshunts to close. When this happens, blood from the core floods into thevery cold tissue on the body surface and extremities, and as a resultthe blood loses heat to those tissues, often far more than the amount ofheat being added by the surface warming. As a result, the victim's coretemperature may plummet and the patient may even go into shock.

Partly in response to the inadequacies of surface application of heat,methods have been developed for adding heat to a patient's body byinternal means. A patient being administered breathing gases, forexample a patient under anesthesia, may have the breathing gases warmed.For some situations, particularly mild hypothermia requiring theaddition of small amounts of heat, this method may be effective, but itis limited in the amount of heat that can be administered withoutinjuring the lungs. Similarly, a patient receiving IV fluids may havethe fluids warmed, or a bolus of warm fluid may be administeredintravenously. Again, this may be effective in the case of mildhypothermia, but the amount of heat that may be added to a patient'sbody is limited because the temperature of the IV fluid is limited to atemperature that will not be destructive to the blood, generally thoughtto be about 41° C.-49° C., and the amount of fluid that is acceptable toadminister to the patient.

A more invasive method may be used to add heat to a patient's blood,particularly in the case of heart surgery. A cannula is attached to avein, usually the inferior vena cava (IVC) of a patient, the veinclamped off and virtually all the patient's blood shunted through thecannula to an external pump. The blood is then pumped back into thepatient's body, generally to the arterial side of the patient'scirculation. Blood removed from a patient may be heated or cooledexternally before it is reintroduced into the patient's body. An exampleof such a by-pass arrangement is the Cardio-Pulmonary By-pass system(CPB) often used in open heart surgery.

This by-pass method, once it is initiated, is both fast and effective inadding or removing heat from a patient's blood and in exercising controlover the patient's body temperature in general, but has the disadvantageof involving a very invasive medical procedure which requires the use ofcomplex equipment, a team of highly skilled operators, is generally onlyavailable in a surgical setting, and because of these complexities,requires a long time to initiate. In fact, it generally cannot beginuntil after the patient's thorax has been surgically opened. For allthese reasons, it is generally not useful for emergency treatment ofhypothermia. By-pass also involves mechanical pumping of blood, which isgenerally very destructive to the blood resulting in cytotoxic andthrombolytic problems associated with removal of blood from the body,channeling the blood through various tubes, artificially oxygenating theblood, and returning the blood subjected to these stresses to thecirculatory system, including the brain. Because of the potentialharmful impact on the patient, most surgeons attempt to limit the time apatient is subjected to by-pass to less than four hours.

Methods for adding heat to the core of the body that do not involvepumping the blood with an external, mechanical pump have been suggested.For example, a method of treating or inducing hypothermia orhyperthermia by means of a heat exchange catheter placed in thebloodstream of a patient was described in U.S. Pat. No. 5,486,208 toGinsburg, the complete disclosure of which is incorporated herein byreference. That patent discloses and claims a method of increasing apatient's body temperature by adding heat to the blood by inserting aheat exchange catheter having a balloon with heat exchange fins into thevascular system and circulating heat exchange fluid through the balloonwhile the balloon is in contact with the blood.

Although accidental hypothermia is generally harmful and requirestreatment, in some instances it may be desirable to induce hypothermiaor permit it to persist in a controlled situation. Hypothermia isgenerally recognized as being neuroprotective and may be induced forthat reason. Neural tissue such as the brain or spinal cord, isparticularly subject to damage by vascular disease processes including,but not limited to ischemic or hemorrhagic stroke, blood deprivation forany reason including cardiac arrest, intracerebral or intracranialhemorrhage, and head trauma. Other where hypothermia may be protectiveinclude treatment of myocardial infarction, and heart surgery,neurosurgical procedures such as aneurysm repair, endovascular aneurysmrepair procedures, spinal surgeries, procedures where the patient is atrisk for brain, cardiac or spinal ischemia such as beating heart by-passsurgery or any surgery where the blood supply to the heart, brain orspinal cord may be temporarily interrupted. In each of these instances,damage to brain tissue may occur because of brain ischemia, increasedintracranial pressure, edema or other processes, often resulting in aloss of cerebral function and permanent neurological deficits.Hypothermia may be intentionally induced because it is advantageous insuch situations. In fact, in some of these situations, such as beatingheart by-pass surgery, hypothermia currently occurs as a normal sideeffect of anesthesia disabling a patient's normal thermoregulatoryresponses in conjunction with prolonged exposure of the chest cavity.The resultant hypothermia may not itself be harmful if adequate controlover the patient's temperature is established, and where the hypothermiccondition is controlled as to depth and duration, it may be permitted topersist or even induced. Control of the depth of hypothermia andreversal of hypothermia after the operation are both important, and ifthat control is not possible, hypothermia is generally thought to beundesireable.

Although the exact mechanism for neuroprotection is not fullyunderstood, lowering the brain temperature is believed to effectneuroprotection through several mechanisms including, the blunting ofany elevation in the concentration of neurotransmitters (e.g.,glutamate) occurring after ischemic insult, reduction of cerebralmetabolic rate, moderation of intracellular calciumtransport/metabolism, prevention of ischemia-induced inhibitions ofintracellular protein synthesis and/or reduction of free radicalformation as well as other enzymatic cascades and even geneticresponses.

Besides its benefit as a prophylactic measure, for example duringsurgery to prevent damage in case of neurologic ischemia, it is alsosometimes desirable to induce whole-body or regional hypothermia for asa treatment in response to certain neurological diseases or disorderssuch as head trauma, spinal trauma and hemorrhagic or ischemic stroke.Hypothermia has also been found to be advantageous as a treatment toprotect both neural tissue and cardiac muscle tissue after a myocardialinfract (MI). Again, the exact mechanism of benefit is not known, butinducing hypothermia in such situations, after the initial ischemicinsult, may lessen damage by decreasing reperfusion injury, interruptingvarious chemical cascades that would otherwise damage the cellsinvolved, protecting membrane integrity and perhaps even preventingcertain genetic changes leading to apoptosis.

Intentionally inducing hypothermia has generally been attempted byeither surface cooling or by-pass pumping. Surface cooling has generallyproved to be unacceptably slow, since the body heat to be removed mustbe transmitted from the core to the surface, and has sometimes beenaltogether unsuccessful since the body's thermoregulatory mechanisms actto oppose any attempt to induce hypothermia and generally succeed inpreventing surface cooling from reducing the core temperature of thebody. For example, the vasoconstriction and AV shunting may prevent heatgenerated in the core from being transmitted to the surface by theblood. Thus the surface cooling may only succeed in removing heat fromthe skin and surface tissue and thus cooling the surface, and notsucceed in reducing the core temperature of the patient.

Another thermoregulatory mechanism that may thwart attempts to reducecore temperature by surface cooling is shivering. There are numeroustemperature sensors on the body's surface, and these may trigger thebody to begin shivering. Shivering results in the generation of asignificant amount of metabolic heat, as much as five times more thanthe resting body, and especially where vasoconstriction and AV shuntingreduce blood to the surface of the body, suface cooling such as by acooling blanket can only reduce the temperature of the patient veryslowly, if at all. Even if the thermoregulatory mechanisms are disabledby anesthesia or other drugs, it has generally been found that thecooling by surface measures such as blankets is unacceptably slow forinducing hypothermia. If the patient has fever and thus an elevated setpoint temperature (the temperature which the body's thermoregulatoryresponses act to maintain), the patient may even shiver at a temperatureabove normothermia. In such situations, it has been found that surfacecooling is often unable to reduce the patient's temperature even tonormothermia. Furthermore, besides often being ineffective and generallybeing unacceptably slow, surface cooling lacks sufficient control overthe target temperature of the patient, since the methods are inadequateto quickly adjust the patient's body temperature and therefore mayresult in overshoot or other uncontrolled body temperature problems thatcannot be adequately managed.

Inducing hypothermia using by-pass techniques is generally effective,fast and controllable, but is also subject to the shortcomings of theby-pass method for adding heat to control accidental hypothermia; itrequires a very invasive procedure in an operating room under fullanesthesia, with intubation, expensive equipment and highly trainedpersonnel. Even in the situation of open heart surgery or neurosurgerywhere the patient is in the operating suite and has highly skilledpersonnel in attendance anyway, the by-pass mechanism requires pumpingthe blood with a mechanical pump through external circuit, which isgenerally thought to be very destructive of the blood and is generallynot maintained for very long, preferably four hours or less, and coolingcannot be begun before the patient's thorax is opened and a shuntsurgically installed, itself a procedure that might induce someneurological ischemia, or continued, nor warming effected, after thepatient's thorax is closed. Thus any advantage of pre-cooling before thepatient is opened, or continued after or re-warmed after the patient isclosed, is not attained by this method, and the patient is exposed tothe undesirable effects of external pumping.

Cold breathing gases and cold infusions have generally not been used toinduce hypothermia. Breathing cold gases is generally ineffective toinduce hypothermia since the lungs are generally structured to be ableto breathe very cold air without rapidly inducing hypothermia. Injectionof cold infusate would generally be unacceptable as a method of inducingand maintaining hypothermia because infusing the large volume of liquidthat would be necessary to induce and maintain hypothermia for a usefullength of time would be unacceptable.

The previously mentioned heat exchanged cathetger placed in thebloodstream of a patient overcomes many of these inadequacies of theother methods of combating accidental hypothermia, or intentionallyinducing hypothermia. Particularly in view of the body's ownthermoregulatory attempts to maintain normothermia, a very efficientheat exchange catheter is highly desirable.

Under certain conditions heat is generated within the body or heat isadded from the environment in excess of the body's ability to dissipateheat, and a persons develops a condition of abnormally high bodytemperature, a condition known as hyperthermia. Examples of thiscondition may result from exposure to a hot and humid environment orsurroundings, overexertion, or exposure to the sun while the body'sthermoregulatory mechanisms are disabled by drugs or disease.Additionally, often as a result of injury or disease, a person mayestablish a set point temperature that is above the normal bodytemperature of about 37° C. a condition generally known as fever. Inanother condition, malignant hyperthermia, a condition not wellunderstood, the body may fail to dissipate enough heat and thetemperature of the body may spiral to dangerous levels without thebody's normal mechanisms being effective to return the patient tonormothermia.

Prolonged and severe hyperthermia may have serious and very negativeeffects. For example, a child with prolonged and high fever as a resultof spinal meningitis might suffer permanent brain damage. In stroke, thepresence of even a mild fever has been found to correlate with verynegative outcome. In such cases, it may be very desirable to counteractthe body's attempt to establish a higher temperature, and instead tomaintain at temperature at or near normothermia. However, the unaidedbody is acting to maintain a temperature above 37° C. and the body's ownthermoregulatory mechanisms, such as AV shunting and shivering mayrender surface cooling altogether ineffective in reestablishingnormothermia. The advantages of an effective core cooling method aresorely needed in such situations.

As with hypothermia, counter-parts to simple methods for treatingundesirable hyperthermia exist, such as cold water baths and coolingblankets, as well as more effective but complex and invasive means suchas cooled breathing gases and blood cooled during by-pass. These,however, are subject to the limitations and complications as describedabove in connection with hypothermia. In addition, as is the case whenattempting to induce hypothermia, the thermoregulatory responses of thebody such as vasoconstriction, AV shunting and shivering, may actdirectly to combat the attempt to cool the patient and thereby defeatthe effort to treat the hyperthermia. In order to achieve the reductionof accidental, diseased or malignant hyperthermia, a catheter withsufficient heat exchange effectiveness to override the body'sthermoregulatory defenses is needed.

For various reasons, it may be desirable to induce and/or maintainhyperthermia. For example, certain cancer cells may be sensitive totemperature elevations, and thus it may be possible to destroy thosecancerous cells by elevating a patient's temperature to a level that istoxic to the cancer cells but the rest of the body can tolerate. Asanother example, a high temperature may be toxic to certain viruses at alevel that the rest of the body can tolerate. Raising the patient'stemperature above that which the virus can tolerate but within atemperature range the body can tolerate would help to rid the body ofthe virus. A heat exchanger that can add heat to the bloodstream of apatient at a sufficient rate to maintain the patient in a state ofhyperthermia would therefore be desirable.

Besides intentionally induced hypothermia or hyperthermia, it issometimes desirable to control a patient's temperature to maintain atarget temperature, sometimes but not always normothermia. For example,in a patient under general anesthesia during major surgery, theanesthesiologist may wish to control the patient's body temperature bydirectly adding or removing heat. In such a situation, the patient'snormal thermoregulatory responses are reduced or eliminated byanesthesia, and the patient may lose an extraordinary amount of heat tothe environment. The patient's unaided body may not generate sufficientheat to compensate for the heat lost and the patient's temperature maydrift lower. The anesthesiologist may wish to control the temperature atnormothermia, or may prefer to allow the patient to become somewhathypothermic, but control the depth and duration of the hypothermia. Adevice and method for precisely controlling body temperature byefficiently adding or removing heat to control a patient's temperaturewould be very desirable.

In addition to controlling the patient's body temperature, fast andprecise control of the adjustments to a patient's thermal condition isvery important when a patient's temperature is being manipulated. Whenusing heat transfer from the surface to the core of a patient as by theapplication of warming or cooling blankets, besides being slow andinefficient, the control of the patient's core temperature is verydifficult, if not impossible. The temperature of the patient tends toAovershoot@ the desired low temperature, a potentially catastrophicproblem when reducing the core temperature of a patient, especially tomoderate or sever levels. The body's own metabolic activity andthermoregulatory responses may make even gross adjustments of coretemperature by surface cooling difficult, slow, or even impossible.Speedy and precise control is generally not possible by such methods atall.

Control of body temperature using by-pass techniques is generally fairlyprecise and relatively fast, especially if large volumes of blood arebeing pumped through the system very quickly. However, as was previouslystated, this method is complex, expensive, invasive and it is this verypumping of large quantities of blood that may be seriously damaging tothe patient, particularly if maintained for any significant period oftime, for example for or more hours.

An efficient heat exchanger might make possible the manipulation oftemperature of a select portion of a patient's body. Generally, thetemperature throughout the body is relatively constant and generallydoes not vary significantly from one location to another. (One exceptionis the skin, which because of exposure to the environment may varysignificantly in temperature. In fact, many of the thermoregulatorymechanisms discussed above depend on the ability of the skin to maintaina different temperature, generally a lower temperature, than thetemperature of the core of the body.) The mammalian body generallyfunctions most efficiently at normothermia. In some instances, however,regional hypothermia or hyperthermia (hypothermia or hyperthermia ofonly a part of the body while the rest of the body is at a differenttemperature, preferably normothermia) may be advantageous. For example,it could be advantageous to cool the head for purposes ofneuroprotection of the brain or cool the heart to protect the myocardiumfrom suffering infarction during or after ischemia, or heating acancerous region to destroy cancerous cells, while maintaining the restof the body at normal, healthy temperature so that the disadvantages ofwhole body hypothermia or hyperthermia would not occur. Additionally,where the entire body is cooled, shivering and other thermoregulatorymechanisms may act to counter attempts to cool the body, and if only aspecific region were targeted for cooling, those mechanisms might beobviated or eliminated.

A heat exchanger in contact with body fluid, such as blood, which wasdirected to the target area, might alter the temperature of that regionif the heat exchanger was efficient enough to cool the bloodsufficiently to cool the tissue in question even if the bodytemperature, i.e. the initial temperature of the blood flowing past theheat exchange region was normothermic. A heat exchange catheter with ahighly efficient heat exchange region would be required for such anapplication. Where the catheter is inserted percutaneously into thevasculature, it is also highly desirable to have as small an insertionprofile as possible to allow as small a puncture as possible, yet allowmaximum surface area of the heat exchange region in contact with theflowing blood. Such a catheter is the subject of this application.

For all the foregoing reasons, there is a need for a means to add orremove heat from the body of a patient in an effective and efficientmanner, while avoiding the inadequacies of surface heat exchange andavoiding the dangers of internal methods including by-pass methods.There is the need for a means of rapidly, efficiently and controllablyexchanging heat with the blood of a patient so the temperature of thepatient or target tissue within the patient can be altered orcontrollably maintained at some target temperature.

Positioning a catheter centrally within the flowing bloodstream may beimportant for various reasons. Contact between a hot or cold heatexchange region and the walls of a body conduit such as a blood vesselmay affect the tissue at the point of contact. In some applications,such as where the user seeks to tack the surface of a dissected vesselto the wall of the vessel, or to thermally treat or ablate the tissue inquestion, the contact between the balloon and the surrounding bodystructure is important, even critical. Where, however, the contact isundesirable, it would be advantageous to have a means to prevent theheat exchange region from resting against the vessel wall.

Where temperature control of the temperature of the blood is the goal,it is also advantageous to position the heat exchange region in thecenter of a flow of body fluid, for example in the center of the lumenof a blood vessel so that the blood flow would surround the entireballoon and no portion of the balloon surface would be sheltered fromthe flow and thus prevented from exchanging heat at the balloon surfacewith the body fluid. This would also help prevent blood to pool in areasof low flow or lack of flow, which has been shown to cause blood toclot.

It would be particularly advantageous if the heat exchange surface couldbe configured to maximize the surface area in contact with the bloodwhile minimizing the obstruction to fluid flow within the vessel. Thisis desirable both because maximum flow is important for maximum heatexchange and because maximum flow will assure that there is adequateblood supply to tissue downstream of the heat exchange region. Thus therate of the blood flow past the heat exchange region should be maximizedat the same time that the surface area of the heat exchange regionwithin the stream of flowing blood is maximized. A catheter that couldachieve these seemingly contradictory goals would be highly desirable.

Additionally, where heat exchange is occurring between two flowingfluids, it is most efficient to have counter-current flow. That is, theflow of the heat exchange liquid is counter to the flow direction of thefluid with which it is exchanging heat. Since a heat exchange cathetermight be inserted into blood vessels in various ways that would resultin the natural blood flowing being different in different instances(i.e. proximal to distal, or distal to proximal) it would advantageousto have a catheter wherein the direction of the fluid flow in theportion of the balloon exposed to the flow of the body fluid could beadjusted to flow in either direction to permit the catheter could beinserted into the blood vessel in either direction, and the direction ofthe flow of the heat exchange fluid adjusted to flow counter to the flowin the vessel.

If the heat exchange catheter is to be inserted into the vasculature ofa patient, it is very advantageous to have a small insertion profile,that is to say a diameter of the device at insertion that is a small aspossible. This permits the insertion of the device through as smallsheath, puncture, or incision. Yet the surface area of the heat exchangeregion should be maximized when the catheter is functioning to exchangeheat with the blood. Once again, these goals seem contradictory, and aheat exchange catheter that could achieve both characteristics would behighly advantageous.

SUMMARY OF THE INVENTION

The present invention provides a heat exchange catheter having a heatexchange region that comprises a balloon having multiple lumens forcirculation of a heat exchange medium and a method for accomplishingintravascular heat exchange by circulation of heat exchange medium fromoutside the body through a multi-lumen shaft and through a multi-lumenballoon having curvilinear (e.g., helical, twisted or other curvedconfiguration) balloon elements such as balloon lobes in contact with apatient's blood.

Further in accordance with the invention, there is provided a heatexchange catheter having a heat exchange region that comprises at leastone balloon having multiple lumens for circulation of a heat exchangemedium and a method for accomplishing intravascular heat exchange bycirculation of heat exchange medium from outside the body through amulti-lumen shaft and through a shaped multi-lumen balloon in contactwith a patient's blood. The method further may include altering thetemperature of the heat exchange fluid outside the body so that it is atemperature different than the temperature of the patient's blood,placing the heat exchange region in contact with the patient's blood,and circulating the heat exchange fluid through the heat exchange regionto exchange heat with the bloodstream at a sufficient rate and for asufficient length of time to effect regional or whole body temperaturemodification of the patient.

Further in accordance with the invention, a heat exchange catheter ofthe invention may comprise a flexible catheter body or shaft having aproximal end and a distal end, the distal end of such catheter shaftbeing adapted to be inserted percutaneously into the vasculature or bodycavity of a mammalian patient. A heat exchange region is provided on thecatheter shaft, comprising a balloon with a plurality of lumenshelically wound around a central axis. (A balloon is defined as astructure that is readily expandable under pressure and collapsibleunder vacuum and includes both elastomeric structures andnon-elastomeric structures that are deformable in the manner described.)The shaft of the catheter preferably includes a fluid circulation pathor lumen, and each heat exchange element preferably is attached at bothends of the shaft and incorporates a fluid circulation path or lumenthat is in fluid communication with the fluid circulation path or lumenof the catheter shaft. In this manner, heat exchange fluid may becirculated into or through the heat exchange region as it iscircumferentially surrounded by the body fluid.

Further in accordance with some embodiments of the invention, the heatexchange region may be less than the length of the portion of thecatheter inserted into the patient and may be located at or near thedistal end thereof. In such embodiments, an insulating region may beformed on the catheter shaft proximal to the heat exchange region toreduce unwanted transfer of heat to and from the proximal portion of thecatheter shaft.

Further in accordance with the present invention, there is provided asystem for heat exchange with a body fluid, the system including a) aliquid heat exchange medium and b) a heat exchange catheter having aheat exchange region comprising a balloon having helicaly formed lumens.The catheter includes a shaft having a proximal end and a distal end,the distal end adapted to be inserted percutaneously into a body cavity.The shaft having a circulation pathway therein for the circulation ofheat exchange medium therethrough. The heat exchange region is attachedto the catheter so that when the catheter is inserted in the bodycavity, body fluid surrounds the heat exchange region.

Further in accordance with the present invention, the heat exchangeregion is deflated for percutaneous insertion into the patient'svasculature to a small diameter, and once positioned with the heatexchanger in the vasculature, the heat exhange region may be inflated toa larger diameter to increase the surface area of the heat exchangeregion for maximum heat exchange with the blood.

The system further may include a sensor or sensors attached to thepatient to provide feedback on the condition of the patient, for examplethe patient's temperature. The sensors are desirably in communicationwith a controller that controls the heat exchange catheter based on thefeedback from the sensors.

Still further in accordance with the present invention, there isprovided a method for exchanging heat with a body fluid of a mammal. Themethod includes the steps of a) providing a catheter that has acirculatory fluid flow path therein and a heat exchange region thereon,such heat exchange region including heat exchange elements that areattached to the catheter shaft at the heat exchange region, b) insertingthe catheter into a body cavity and into contact with a body fluid, theheat exchange elements thus being surrounded by the body fluid and c)causing a heat exchange medium to flow through the circulatory flow pathof the catheter so that the medium exchanges heat with a body fluidthrough the heat exchange elements. Each of the heat exchange elementsmay be hollow balloon lobes, and step C of the method may includecausing heat exchange fluid to flow through the hollow heat exchangeelements.

It is an object of this invention to provide an effective andadvantageous heat exchange region for adding heat to a patient sufferingfrom hypothermia.

It is a further object of this invention to provide an effective meansfor removing heat from the bloodstream of a patient suffering fromhyperthermia.

It is a further object of this invention to provide an effective meansof adding or removing heat from a patient to induce normothermia.

It is a further object of this invention to provide an effective meansfor maintaining normothermia.

It is a further object of this invention to provide an effective meansof cooling a patient to a target temperature and controllablymaintaining that temperature.

It is a further object of this invention to provide a heat exchangecatheter that has an advantageous configuration that provides formaximum heat exchange with blood flowing in heat exchange proximity tothe heat exchange region.

It is a further object of this invention to provide a heat exchangecatheter that has an advantageous shape that attains an advantageousratio of heat exchange surface area while maintaining adequate flow in ablood vessel.

It is a further object of this invention to provide a catheter with asufficiently effective and efficient heat exchange region to cool atarget region of a patient.

It is a further object of this invention to provide a catheter with asufficiently effective and efficient heat exchange region to preciselymaintain a patient at a target temperature.

It is a further object of this invention to provide a heat exchangecatheter that is configured to efficiently exchange heat with the bloodof a patient while allowing continued flow of the blood past thecatheter with a minimum of restriction to that blood flow.

It is a further object of this invention to provide a heat exchangecatheter having a heat exchange region comprised of multiple balloonelements such as lobes.

It is a further object of this invention to provide a heat exchangecatheter having an insulated shaft.

It is a further object of this invention to provide an effective methodof controlling the temperature of a body fluid.

It is a further object of this invention to provide an effective methodof warming a body fluid.

It is a further object of this invention to provide an effective methodof cooling a body fluid.

It is a further object of this invention to provide an effective methodfor inducing hypothermia.

It is a further object of this invention to provide a catheter having aheat exchange region wherein the temperature is controlled by thetemperature of flowing heat exchange fluid and wherein the direction ofthe fluid flow may be reversed.

It is a further object of this invention to provide a heat exchangecatheter having a heat exchange region wherein, when the heat exchangeregion is placed within a blood vessel, the shape of the heat exchangeregion assists in centering the heat exchange region within the vessel.

It is a further object of this invention to provide a heat exchangecatheter having a heat exchange region composed of multiple, non-coaxialballoon elements such as lobes of a multi-lobed balloon.

These and other objects of this invention will be understood withreference to the following drawings and description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective drawing of an embodiment of the catheter of theinvention.

FIG. 1A is a perspective drawing of an alternative tie-down at theproximal end of the catheter shown in FIG. 1.

FIG. 2 is a cross-sectional drawing of the shaft of the catheter takenalong the line 2-2 in FIG. 1.

FIG. 3 is a cross-sectional drawing of the heat exchange region of thecatheter taken along the line 3-3 in FIG. 1.

FIG. 3A is a cross-sectional drawing of the heat exchange region of thecatheter taken along the line 3A-3A in FIG. 1.

FIG. 4 is a perspective drawing of a segment of the heat exchange regionof the catheter within the circle 4-4 in FIG. 1.

FIG. 5 is a cross-sectional drawing of the heat exchange region of thecatheter taken along the line 5-5 in FIG. 1.

FIG. 6 is a perspective drawing of a segment of the heat exchange regionof the catheter within the circle 6-6 in FIG. 1.

FIG. 7 is a perspective drawing of the multi-lobed balloon of oneembodiment of the invention.

FIG. 8 is a perspective drawing of the distal portion of the shaft ofone embodiment of the invention.

FIG. 9 is a perspective drawing, partially in ghost, of the heatexchange region formed by the shaft and multi-lobed balloon of FIGS. 7and 8.

FIG. 10 is an expanded view of the attachment of the central lumen ofthe balloon to the shaft of the catheter of FIG. 9 showing the regionwithin the circle 10-10 in FIG. 9.

FIG. 10A is an expanded view of the plug between the shaft and thecentral lumen of the balloon of the catheter of FIG. 9 showing theregion within the circle 10A-10A in FIG. 9.

FIG. 11 is a perspective view of a portion of a multi-lobed curvilinearheat exchange balloon of one embodiment of the invention.

FIG. 11A is a cross sectional view of the heat exchange region takenalong the line 11A-11A in FIG. 11.

FIG. 12 is a sectional view of the proximal portion of the heat exchangeregion of one embodiment of the invention.

FIG. 12A is a cross-sectional view of a portion of the heat exchangeregion taken along the line 12A-12A of FIG. 12.

FIG. 12B is a cross-sectional view of a portion of the heat exchangeregion taken along the line 12B-12B of FIG. 12.

FIG. 12C is a cross-sectional view of a portion of the heat exchangeregion taken along the line 12C-12C of FIG. 12.

FIG. 13 is a sectional view of the distal portion of the heat exchangeregion of one embodiment of the invention.

FIG. 13A is a cross-sectional view of a portion of the heat exchangeregion taken along the line 13A-13A of FIG. 13.

FIG. 13B is a cross-sectional view of a portion of the heat exchangeregion taken along the line 13B-13B of FIG. 13.

FIG. 14 is a sectional view of the distal portion of the heat exchangeregion of one embodiment of the invention.

FIG. 15A is a side view, partially in ghost, of the heat exchange regionof one embodiment of the invention.

FIG. 15B is a cross-section taken along the line 15B-15B in FIG. 15A.

FIG. 15C is a cross-section taken along the line 15C-15C in FIG. 15A.

FIG. 15D is a cross-section taken along the line 15D-15D in FIG. 15A.

FIG. 15E is a cross-section taken along the line 15E-15E in FIG. 15A.

FIG. 15F is a cross-section taken along the line 15F-15F in FIG. 15A.

FIG. 16A is a perspective view of one embodiment of an intavascular heatexchange catheter according to the present invention.

FIG. 16B is a front perspective view of one embodiment of anextracorporeal temperature control console that is useable inconjunction with the catheter of FIG. 16A to accomplish temperaturemanagement of a human or veterinary patient.

FIG. 17 is a flowchart of an exemplary method of the invention.

DETAILED DESCRIPTION

The present invention provides an improved heat exchange catheter thatprovides an efficient and effective heat exchange region to exchangeheat with body fluid while maintaining a minimum insertion profile ofthe catheter. The heat exchange catheter generally comprises a catheterhaving a shaft for the flow of heat exchange fluid to and from a heatexchange region, and the heat exchange region comprising anadvantageously configured multiple lumen balloon wherein the heatexchange fluid flows through the balloon and blood flows over theoutside of the balloon and heat is exchanged through the walls of theballoon between the heat exchange fluid flowing inside the balloon andthe blood flowing outside the balloon.

Referring to FIGS. 1 through 10A, in one advantageous embodiment, thecatheter is comprised of a shaft 50 with a heat exchange region 100thereon.

The shaft has two roughly parallel lumens running through the proximalshaft, an inflow lumen 52 and an outflow lumen 54. The shaft generallyalso comprises a working lumen 56 running therethrough for the insertionof a guide wire, or the application of drugs, radiographic dye, or thelike to the distal end of the catheter. The heat exchange regioncomprises a four-lumen balloon, with three outer lumens 58, 60, 62disposed around an inner lumen 64 in a helical pattern. In theparticular embodiment shown, the balloon preferable makes one fullrotation about the inner lumen 64 for each 2 to 4 inches of length. Allfour lumens are thin walled balloons and each outer lumen shares acommon thin wall segment 66, 68, 70 with the inner lumen. The balloon isapproximately twenty-five centimeters long, and when inflated has anouter circumference 72 of approximately 0.328 in. When deflated, theprofile is generally less than about 9 French (3 French is 1 mm indiameter). When the balloon portion is installed on the shaft, both theballoon proximal end 74 and the distal end 76 are sealed around theshaft in a fluid tight seal as will be described below.

The catheter is attached at its proximal end to a hub 78. At the hub,the guide wire lumen 56 communicates with a guide wire port 80, theinflow lumen 52 is in fluid communication with an inflow port 82, andthe outflow lumen 54 is in communication with an outflow port 84.Attached at the hub and surrounding the proximal shaft is a length ofstrain relief tubing 86 which may be, for example, a length of heatshrink tubing. The strain relief tubing may be provided with suture tiedowns 88, 90. Alternatively, a butterfly tie-down 92 may be provided.(See FIG. 1A). Between the strain relief tubing 86 and the proximal endof the balloon 74, the shaft 50 is extruded with an outer diameter ofabout 0.118 inches. The internal configuration is as shown incross-section in FIG. 2. Immediately proximal of the balloon attachment74, the shaft is necked down 94.

The outer diameter of the shaft is reduced to about 0.100 to 0.110inches, but the internal configuration with the three lumens ismaintained. Compare, for example, the shaft cross-section of FIG. 2 withthe cross-section of the shaft shown in FIG. 3. This length of reduceddiameter shaft remains at approximately constant diameter of about 0.100to 0.110 inches between the necked down location at 94 and the distallocation 96 where the outflow lumen is sealed and the guide wireextension tube 98 is attached as will be described.

At the necked down location 94, a proximal balloon marker band 102 isattached around the shaft. The marker band is a radiopaque material suchas a platinum or gold band or radiopaque paint, and is useful forlocating the proximal end of the balloon by means of fluoroscopy whilethe catheter is within the body of the patient.

At the marker band, all four lobes of the balloon are reduced down andfastened to the shaft 50. This may be accomplished by folding the outerlobes of the balloon 58, 60, 62 down around the inner lumen 64, placinga sleeve, for example a short length of tubing, over the balloon andinserting adhesive, for example by wicking the adhesive, around theentire inner circumference of the sleeve. The inner lumen is thenfastened to the shaft using a second short length of tubing. A shortlength for example 1 mm, of intermediate tubing 104 is heat welded tothe inside of the inner lumen. The intermediate tube has an outerdiameter approximately the same as the inner diameter of the innerlumen. The intermediate tube is then slid over the shaft at about thelocation of the neck-down near the proximal marker 102 and adhesive 106is wicked into the space between the inside of the intermediate tubingand the outer surface of the shaft 50.

A similar process may be used to attach the distal end o the balloon.The distal end of the balloon is attached down around the guide wireextension tube 98 rather than the shaft, but otherwise the attachment isessentially similar.

Distal of the proximal balloon seal, under the balloon, an elongatedwindow 108 cut through the wall of the outflow lumen in the shaft. Alongthe proximal portion of the balloon, five slits, e.g. 110, are cut intothe common wall between each of the outer lumens 58, 60, 62 and theinner lumen 64. Because the outer lumens are twined about the innerlumen in a helical fashion, each of the outer tubes passes over theoutflow lumen of the inner shaft member at a slightly different locationalong the length of the inner shaft, and therefore an elongated window108 is cut into the outflow lumen of the shaft so that each outer lumenhas at least one slit e.g. 110 that is located over the window in theshaft. Additionally, there is sufficient clearance between the outersurface of the shaft and the wall of the inner lumen to createsufficient space to allow relatively unrestricted flow through heatexchange fluid through all 5 slits in each outer lumen, around theshaft, and through the elongate window 108 into the outflow lumen 54 inthe shaft 50.

Distal of the elongated window in the outflow lumen, the inner member 64of the four-lumen balloon is sealed around the shaft in a fluid tightplug. Referring to FIG. 10a , the plug is formed by, for exampleshrinking a relatively thick length of PET tubing to form a length ofplug tubing 112 where the inner diameter of the length of plug tubing isapproximately the same as the outer diameter of the shaft at thelocation where the plug is to be formed. The plug tubing is slid overthe shaft and fits snugly against the shaft. The shaft is generallyformed of a material that is not heat shrinkable. As may be seen in FIG.10A and FIG. 3, some clearance exists between the outer wall of theshaft and the inner wall of the inner lumen 64. The walls of the innerlumen are composed of thin heat shrinkable material, for example PET. Aprobe with a resistance heater on the distal end of the probe isinserted into the guide wire lumen of the shaft and located with theheater under the plug tubing. The probe is heated, causing the heatshrink wall of the inner lumen to shrink down against the plug tubing,and the plug tubing to shrink slightly down against the shaft. Theresultant mechanical fit is sufficiently fluid tight to prevent theoutflow lumen and the space between the shaft and the wall of the innerlumen from being in fluid communication directly with the inner memberor the inflow lumen except through the outer lumens as will be detailedbelow.

Just distal of the plug, the outflow lumen is closed by means of heatsealing 99, and the inflow lumen is skived open to the inner member 101.This may be accomplished by necking down the shaft at 96, attaching aguide wire extension tube 98 to the guide wire lumen, and at the samelocation opening the inflow lumen to the interior of the inner lumen andheat sealing the outflow lumen shut. The guide wire extension tubecontinues to the distal end of the catheter 114 and thereby createscommunication between the guide wire port 80 and the vessel distal ofthe catheter for using a guide wire to place the catheter or forinfusing drugs, radiographic dye, or the like beyond the distal end ofthe catheter.

The distal end of the balloon 76 is sealed around the guide wireextension tube in essentially the same manner as the proximal end 74 issealed down around the shaft. Just proximal of the distal seal, fiveslits 116 are cut into the common wall between each of the three outerlumens 58, 60 62 of the balloon and the inner lumen 64 so that each ofthe outer lumens is in fluid communication with the inner lumen.

Just distal of the balloon, near the distal seal, a distal marker band118 is placed around the guide wire extension tube. A flexible length oftube 120 may be joined onto the distal end of the guide wire tube toprovide a soft tip to the catheter as a whole.

In use, the catheter is inserted into the body of a patient so that theballoon is within a blood vessel, for example in the inferior vena cava(IVC). Heat exchange fluid is circulated into the inflow port 82,travels down the inflow lumen 52 and into the inner lumen 64 distal ofthe plug tube 112. The heat exchange fluid travels down the inner lumen,thence through slits 116 between the inner lumen 64 and the three outerlumens 58, 60, 62.

The heat exchange fluid then travels back through the three outer lumensof the balloon to the proximal end of the balloon. A window 108 is cutin the outflow lumen of the shaft proximal of the plug 99. in the distalportion of the balloon, approximately above the window, about five slits110 are cut in the wall between each of the outer balloon lumens 58, 60,62 and the inner lumen 64.

Since the outer lumens are wound in helical pattern around the innerlumen, at some point at least one of the slits from each of the outerlumens is located directly over the window 108 in the outflow lumen.Additionally, there is sufficient clearance between the wall of theinner lumen and the shaft, as illustrated at 102 in FIG. 10A, that evenif the slits are not directly over the window 108, flow into the spacebetween the wall of the inner lumen and the outer wall of the shaft 50allows the fluid to flow ultimately into the window 108 and out theoutflow lumen without undue resistance. It then flows out the outflowlumen and out of the catheter through the outflow port 84. The fluid maybe pumped at a pressure of, for example, 40-50 pounds per square inch(psi), and at a pressure of about 41 psi, a flow of as much as 500milliliters per minute may be achieved.

Counter-current circulation between the blood and the heat exchangefluid is highly desirable for efficient heat exchange between the bloodand the heat exchange fluid. Thus if the balloon is positioned in avessel where the blood flow is in the direction from proximal toward thedistal end of the catheter, for example if it were placed from thefemoral vein into the ascending vena cava, it is desirable to have theheat exchange fluid in the outer balloon lumens flowing in the directionfrom the distal end toward the proximal end of the catheter. This isachieved by the arrangement described above. It is to be readilyappreciated. however, that if the balloon were placed so that the bloodwas flowing along the catheter in the direction from distal to proximal,for example if the catheter was placed into the IVC from a jugularinsertion, it would be desirable to have the heat exchange fluidcirculate in the outer balloon lumens from the proximal end to thedistal end. Although in the construction shown this is not optimal andwould result is somewhat less effective circulation; this could beaccomplished by reversing which port is used for inflow direction andwhich for outflow.

Where heat exchange fluid is circulated through the balloon that iscolder than the blood in the vessel into which the balloon is located,heat will be exchanged between the blood and the heat exchange fluidthrough the outer walls of the outer lumens, so that heat is absorbedfrom the blood. If the temperature difference between the blood and theheat exchange fluid (sometimes called ΔT), for example if the blood ofthe patient is about 37° C. and the temperature of the heat exchangefluid is about 0° C., and if the walls of the outer lumens conductsufficient heat, for example if they are thin (0.002 inches or less) ofa plastic material such as polyethylene terephthalate (PET), enough heatmay be exchanged (for example about 200 watts) to lower the entire bodytemperature of the patient at a useful rate, for example 3-6° C. perhour.

The helical structure of the outer lumens has the advantage overstraight lumens of providing greater length of heat exchange fluid pathfor each length of the heat exchange region. It may also provide forenhanced flow patterns for heat exchange between flowing liquids.Additionally, the helical shape may assist in maintaining flow in aroughly tubular conduit, for example blood flow in a blood vessel, bynot creating a firm seal around the heat exchange region since theexterior of the heat exchange region is not tubular.

The fact that the heat exchange region is in the form of an inflatableballoon also allows for a minimal insertion profile, for example 9French or less, while the heat exchange region may be inflated onceinside the vessel for dramatically increased functional diameter of theheat exchange region in operation. After use, the balloon can becollapsed for easy withdrawal.

Such a configuration is adequately efficient in heat exchange, the useof a system which controls the temperature of the heat exchange fluidwhich system is directed in response to signals representing thetemperature of a patient is adequate to exercise control over the bodytemperature of a patient.

Referring now to FIGS. 11 through 13B, in another example of a preferredembodiment, the heat exchange region is in the form that may be called atwisted ribbon. The heat transfer fluid circulates to and from the heatexchange region 202 via channels formed in the shaft 206 in much thesame manner as previously described for shaft 50. FIGS. 11 and 11Aillustrate this embodiment of a heat exchange region 202 comprising aplurality of balloon elements in the form of tubular members that arestacked in a helical plane.

More specifically, a central tube 220 defines a central lumen 222therewithin. A pair of smaller intermediate tubes 224 a, 224 b attachesto the exterior of the central tube 220 at diametrically opposedlocations. As illustrated here, the tubes are attached or alternativelyextruded in a unitary extrusion so that the balloon elements formessentially the lobes of a multi-lobed balloon.

Each of the smaller tubes 224 a, 224 b defines a fluid lumen 226 a, 226b therewithin. A pair of outer tubes 228 a, 228 b attaches to theexterior of the intermediate tubes 224 a, 224 b in alignment with thealigned axes of the central tube 220 and intermediate tubes 224 a, 224b. Each of the outer tubes 228 a, 228 b defines a fluid lumen 230 a, 230b within. By twisting the intermediate and outer tubes 224 a, 224 b, 228a, 228 b around the central tube 220, the helical ribbon-likeconfiguration of FIG. 11 is formed.

An inflow path of heat exchange medium is provided by the central tube220, as described in greater detail below. The intermediate tubes 224 a,224 b and outer tubes 228 a, 228 b define a fluid outflow path withinthe heat exchange region 202. Heat exchange fluid is transferred intothe catheter through an inflow port of a hub at the proximal end of theshaft and after circulation is removed via an outflow port inessentially the same manner as previously described. Likewise, a guidewire port is provided on the hub.

Now with reference to FIGS. 12 and 12A-12C, a proximal manifold of theheat exchange region 202 will be described. The shaft 206 extends ashort distance, desirably about 3 cm, within the central tube 220 and isthermally or adhesively sealed to the interior wall of the central tubeas seen at 250. As seen in FIG. 12A, the shaft 206 includes a planarbulkhead 252 that generally evenly divides the interior space of theshaft 206 into an inflow lumen 254 and an outflow lumen 256. A workingor guide wire lumen 260 is defined within a guide wire tube 262 that islocated on one side of the shaft 206 in line with the bulkhead 252.Desirably, the shaft 206 is formed by extrusion.

The outflow lumen 256 is sealed by a plug 264 or other similar expedientat the terminal end of the shaft 206 within the central tube 220. Theinflow lumen 254 remains open to the central lumen 222 of heat exchangeregion 202.

The guide wire tube 262 continues a short distance and is heat bonded at270 to a guide wire extension tube 272 generally centered within thecentral tube 220.

A fluid circulation path is illustrated by arrows in FIG. 12 andgenerally comprises fluid passing distally through the inflow lumen 254and then through the entirety of the central lumen 222. Fluid returnsthrough the lumens 226 a, 226 b, and 230 a, 230 b of the intermediateand outer tubes 224 a, 224 b, and 228 a, 228 b, respectively, and entersreservoirs 274 and 275. These reservoirs are in fluid communication witheach other, forming essentially one terminal reservoir in fluidcommunication with one window 276 in the outflow lumen. Alternatively,two windows may be formed 276 and a counterpart not shown in FIG. 12 onehelical twist farther down the shaft, between each side of the twistedribbon (i.e., lumens 224 a and 224 b on one side, and 228 a and 228 b onthe other side). In this way, one reservoir from each side of thetwisted ribbon is formed in fluid communication with the outflow lumen256, each through its own window (configuration not shown). Fluid thenenters the outflow lumen 256 through apertures, e.g., 276, provided inthe central tube 220 and a longitudinal port 278 formed in the wall ofthe shaft.

A distal manifold of the heat exchange region 202 is shown and describedwith respect to FIGS. 13 and 13A-13B. The outer tubes 228 a, 228 b taperdown to meet and seal against the central tube 220 which, in turn,tapers down and seals against the guide wire extension tube 272. Fluidflowing distally through the central lumen 222 passes radially outwardthrough a plurality of apertures 280 provided in the central tube 220.The apertures 280 open to a distal reservoir 282 in fluid communicationwith lumens 226 a, 226 b, and a distal reservoir 281 in fluidcommunication with lumens 230 a, 230 b of the intermediate and outertubes 224 a, 224 b, and 228 a, 228 b.

With this construction, heat exchange fluid introduced into the inputport 240 will circulates through the inflow lumen 254, into the centrallumen 222, out through the apertures 280, and into the distal reservoir282. From there, the heat exchange fluid will travel proximally throughboth intermediate lumens 226 a, 226 b and outer lumens 230 a, 230 b tothe proximal reservoirs 274 and 275. Fluid then passes radially inwardlythrough the apertures 276 and port 278 into the outflow lumen 256. Thenthe fluid circulates back down the shaft 206 and out the outlet port.

The twisted ribbon configuration of FIGS. 11-13C is advantageous forseveral reasons. First, the relatively flat ribbon does not take up asignificant cross-sectional area of a vessel into which it is inserted.The twisted configuration further prevents blockage of flow through thevessel when the heat exchange region 202 is in place. The helicalconfiguration of the tubes 224 a, 224 b, 228 a, 228 b also aids tocenter the heat exchange region 202 within a vessel by preventing theheat exchange region from lying flat against the wall of the vesselalong any significant length of the vessel. This maximizes heat exchangebetween the lumens and the blood flowing next to the tubes. It alsohelps prevent thermal injury to the vessel wall by avoiding prolongedcontact between a specific location on the vessel wall and the heatexchange region of the catheter. Because of these features, the twistedribbon configuration is ideal for maximum heat exchange and blood flowin a relatively small vessel such as the carotid artery. As seen in FIG.11A, an exemplary cross-section has a maximum functional diameter 300 ofabout 5 mm, permitting treatment of relatively small vessels.

The deflated profile of the heat exchange region is small enough to makean advantageous insertion profile, as small as 7 French for someapplications. Even with this low insertion profile, the heat exchangeregion is efficient enough to adequately exchange heat with bloodflowing past the heat exchange region to alter the temperature of theblood and affect the temperature of tissue downstream of the heatexchange region. Because of its smaller profile, it is possible toaffect the temperature of blood in smaller vessels and thereby providetreatment to more localized body areas.

This configuration has a further advantage when the heat exchange regionis placed in a tubular conduit such as a blood vessel, especially wherethe diameter of the vessel is approximately that of the major axis(width) of the cross section of the heat exchange region. Theconfiguration tends to cause the heat exchange region to center itselfin the middle of the vessel. This creates two roughly semicircular flowchannels within the vessel, with the blood flow channels divided by therelatively flat ribbon configuration of the heat exchange region. It hasbeen found that the means for providing maximum surface for heatexchange while creating minimum restriction to flow is thisconfiguration, a relatively flat heat exchange surface that retains twoapproximately equal semi-circular cross-sections. This can be seen inreference to FIG. 11A if the essential functional diameter of the dashedcircle 300 is essentially the same as a vessel into which the twistedribbon is placed. Two roughly semi-circular flow paths 302, 304 aredefined by the relatively flat ribbon configuration of the heat exchangeregion, i.e. the width or major axis (from the outer edge of 228 a tothe outer edge of 228 b) is at least two times longer than the height,or minor axis (in this example, the diameter of the inner tube 222) ofthe overall configuration of the heat exchange region. It has been foundthat if the heat exchange region occupies no more than about 50% of theoverall cross-sectional area of the circular conduit, a highlyadvantageous arrangement of heat exchange to flow is created. Thesemi-circular configuration of the cross-section of the flow channels isadvantageous in that, relative to a round cross-sectioned heat exchangeregion (as would result from, for example, a sausage shaped heatexchange region) the flow channels created minimize the surface to fluidinterface in a way that minimizes the creation of laminar flow andmaximizes mixing.

Maximum blood flow is important for two reasons. The first is thatmaximum flow downstream to the tissue is important, especially if thereis obstruction in the blood flow to the tissue, as would be the case inischemic stroke or an MI. The second reason is that heat exchange ishighly dependent on the rate of blood flow past the heat exchangeregion, with the maximum heat exchange occurring with maximum bloodflow, so maximum blood flow is important to maximizing heat transfer.

A third exemplary embodiment is very similar to the twisted ribbonembodiment just described, except that the outermost tubes 230 a′, 230b′ are shorter than the intermediate tubes 226 a′, 226 b′, and terminateshort of the intermediate tubes, and therefore the heat exchange regionhas a staggered diameter. Such a construction is illustrated in FIG. 14.The configuration of the shaft and the proximal portion of the balloonare essentially the same as the twisted ribbon catheter just described.However, on the distal end of the heat exchange region, the centrallumen 220′ is manifolded to the intermediate lumens 226 a′ and 226 b′ byslits, for example 280′. The outer lumens 230 a′ and 230 b′, however, donot extend all the way to the distal location where the intermediatetubes are manifolded to the central lumen. Instead, at a locationproximal of the distal end of the intermediate tube, the wall betweenthe outer lumens and the intermediate lumens are cut 295′ so that theouter and intermediate lumens are manifolded to be in fluidcommunication with each other. In this way, heat exchange fluid may beintroduced into the inflow port, flow down the inflow lumen to thecentral lumen, exit the central lumen through slits into theintermediate lumen. The heat exchange fluid then travels proximatelydown the intermediate lumen for some distance to the point where theouter lumens are in fluid communication with the intermediate lumensthrough slits 295′. The heat exchange fluid travels proximally down boththe intermediate lumen and the outer lumen to the proximal manifold,which is essentially the same as described in the previous embodimentand illustrated in FIG. 12. According to this construction, a very smalldiameter heat exchange region can be placed very distal in a smallvessel, and yet a larger diameter heat exchange region be locatedproximally in a larger vessel or a larger diameter portion of the vesselinto which the distal portion of the staggered diameter heat exchangeregion is located. The lengths of the various lumens illustrated in FIG.14 is not meant to be literal, and it will readily be appreciated thatthe lengths and diameters of the lumens may be adjusted to achieve theconfiguration that may be desired for various applications. In someapplications as will be readily appreciated by those of skill in theart, more than merely two lumens may be similarly stacked to achieve aconfiguration with one, two, three or even more steps in diameter of theheat exchange region.

In any configuration, for maximum heat exchange results, it is importantthat the difference in temperature between the blood and heat exchangeregion be as large as possible. Because of the long length of catheterrequired for selective cooling of the brain within the carotid artery inconjunction with femoral insertion, maximum thermal insulation of theshaft is important to maximize heat transfer with the blood flowing tothe brain and minimize heat transfer with the blood flowing away fromthe brain. In use, the catheter is generally passed through a vessel ofrelatively large diameter, for example the Vena Cava or the abdominalaorta, so that there is room within the vessel around the proximal shaftto utilize an inflatable insulating region around the shaft. Such aninflatable region is more fully described in parent application Ser. No.09/489,142 filed Jan. 21, 2000, Titled Heat Exchange Catheter withImproved Insulated Region of which this application is a Continuation inPart and which has previously been incorporated in full by reference.Because the insulating region 204 is deflated at insertion, and inflatedthereafter, the incision or puncture into the vasculature is minimizedbut once inflated, the insulation is maximized. The insulation regionis, of course, deflated for removal.

An alternative construction to the heat exchange balloon is illustratedin FIGS. 15A through 15F wherein the heat exchange region is formed of afour lobed balloon, the balloon having three collapsible outer balloonlobes 902, 904, 906 located in roughly linear and parallel configurationaround a central collapsible lumen 908. The catheter has a proximalshaft 910 formed having two lumens running the length of the shaft, thefirst lumen forming an inlet channel 912 and the second lumen forming anoutlet channel 914. The interior of the shaft is divided into the twolumens by webs 916, 917, but the lumens do not occupy equal portions ofthe interior of the shaft. The inlet channel occupies about ⅓ of thecircumference of the interior; the outlet channel occupies about ⅔ ofthe circumference of the interior for reasons that will be explainedbelow. A guide wire lumen 929 is formed running down the center of theshaft.

Within the proximal portion of the heat exchange region of the catheter,the shaft is affixed to the balloon. A transition region 915 is formedbetween the shaft 910 and the tube 911 forming the central collapsiblelumen 908. The outlet channel is plugged 917, the tube 911 is affixedover the shaft 910 by, for example gluing, at the transition 915, andthe shaft ends. A guide wire extension tube 930 is attached to the guidewire lumen 929 with the guide wire tube running to the distal end of thecatheter. Alternatively, the outer wall of the shaft may be removed atthe transition region, leaving only the tube which forms the guide wirelumen intact.

After the outlet lumen is plugged 917 and the shaft attached to theinterior of the tube which forms the central lumen of the balloon, withthe inlet channel open into the interior of the central lumen, as shownat FIG. 15C, the inlet channel is then occupies the entire inner lumenof the balloon 908 except for the guide wire extension tube 930.

At the distal end of the balloon, inlet orifices 918, 920, 922 areformed between the inlet channel and the three collapsible balloon outerlobes 902, 904, 906. At the proximal end of the heat exchange region,outlet orifices 924, 926, 928 are formed between the interior of eachouter balloon lobe and the outlet channel 914 in the shaft. These may beformed by, for example, cutting or burning holes in the common wallbetween the central lumen and the outer balloon lobes and simultaneouslythrough the wall of the shaft over the outlet lumen. As may be seen inFIG. 15D, the configuration of the outlet channel is such that the wallof the outlet channel occupies a sufficient circumference of the shaft,as noted above, that communication between the outlet channel and theinterior of each of the three outer balloon lobes may be created.

As may be appreciated, in use, heat exchange fluid may be introducedinto the inlet channel through an inlet port (not shown), flow down theinlet channel in the shaft 912 and into the central lumen of the balloon908. It then flows to the distal end of the heat exchange region,through the inlet orifices 918, 920, 922 in the common wall between thecentral lumen and the three outer balloon lobes and flows into theinterior lumens of the balloon lobes 919, 921, 923, travel back downeach of the three balloon lobes and re-enter the shaft through theoutlet orifices 924, 926, 928. The heat exchange fluid then flows downthe outlet channel 914 to the proximal end of the catheter. In this wayheat exchange fluid may be circulated through the three outer balloonlobes to add heat to the blood flowing in heat transfer proximity to theballoons if the heat exchange fluid is warmer than the blood, or toremove heat from the blood if the heat exchange fluid is cooler than theblood.

The balloon is formed from a material that will permit significantthermal exchange between the heat exchange fluid on the interior of theballoon and the body fluid flowing over the outside of the balloon inheat exchange proximity to the surface of the balloon. One suchappropriate material is very thin plastic material such as PET, whichmay also be made strong enough to withstand the pressure necessary foradequate flow of the heat exchange fluid while at the same time beingthin enough, perhaps less than 2 mils (0.002 inches).

It may also readily be appreciated that the same heat exchange balloonsof the various types described herein may be used to add heat to theblood stream or remove heat from the blood stream depending on therelative temperature of the heat exchange fluid and the blood flowing inheat exchange proximity to the balloon. That is, the same device at thesame location may be used alternately to add or to remove heat merely bycontrolling the temperature of the heat exchange fluid within thedevice. When attached to a control unit that can alter the temperatureof the heat exchange fluid in response to an external signal, forexample a sensed temperature of a patient in which the catheter has beenplaced, the device may be used to automatically control the temperatureof the patient.

As previously described, precise control over a patient's temperature ishighly desirable. Because the heat exchange regions of the catheters ofthis invention are highly efficient and are able to add or remove heatfrom a patient with great speed and effectiveness, very precise controlover the temperature of a patient is possible. Precise control, forexample with a precision of one or two tenths of a degree Celsius, ispossible using a heat exchange catheter of this invention and a feedbackcontrol mechanism as illustrated in FIG. 16. In that example, areservoir of heat exchange fluid is placed in contact with a heater orcooler, for example thermoelectric coolers (TEC) located within thecontroller box 600 but not illustrated. A source of heat exchange liquid602, for example saline, is attached the reservoir to supply heatexchange fluid to the system. A pump within the controller boxcirculates the fluid through the reservoir and out the outflow line 604which directs the heated or cooled fluid to the inflow port 82 of thecatheter. After the fluid circulates through the catheter as describedearlier, it returns to the reservoir through the inflow line 606, whichreceives fluid from the outflow port 84 of the catheter hub. The fluidis then circulated through the reservoir in contact with the heater orcooler, which heats or cools the fluid, and is then recirculated in aclosed loop back through the catheter.

Temperature probes 608, 610 are placed on or in the patient so that theygenerate a signal that represents the temperature of the patient of theportion of the patient that is controlled by the system. A single probemay be used, but dual probes may also be used, for example to providefor redundancy as a safety measure. Those probes may be tympanictemperature probes, esophageal probes, rectal probes, temperature probesfor measuring the temperature of the patient's blood, myocardialtemperature probes, or any other probes that will generate a signalrepresentative of the temperature sought to be controlled by the systemwhich may be, for example, a temperature of a target tissue or core bodytemperature. Skin temperature probes are generally not sufficientlyaccurate or free from environmental influences to act as control probesfor this system. However there is no fundamental reason why such probescould not be used, and if they were sufficiently accurate, even surfacetemperature probes would suffice.

A series of desired control parameters are manually input into amicroprocessor control unit such as a dedicated computer in the controlunit, via the user input interface 612. The parameters may include forexample, the desired patient temperature and the rate of warming orcooling. The temperature probes 610, 608 provide patient temperaturesignals to the temperature input terminals 614, 616. The computer thencontrols the temperature of the heat exchange fluid based on the desiredparameters as input by the user and the temperature signal as input bythe temperature probes.

The controller might, for example, add heat to the heat exchange fluidto either warm the patient or reduce the rate of cooling. Similarly, thecontroller might reduce the temperature of the heat exchange fluid tocool the patient or to reduce the rate of warming, depending on thecurrent temperature of the heat exchange fluid and the desiredparameters.

A method is also disclosed for warming, cooling or controlling a patientusing the system disclosed here. That method entails placing a catheterof the invention with the heat exchange region in the bloodstream of apatient. Temperature probes are placed to sense the temperature of thepatient or the target tissue in question. A controller is provided thatcan control the heat exchange between the catheter and the blood by, forexample, controlling the temperature of heat exchange region. In thecatheters of this invention that comprises controlling the temperatureof or rate of flow of the heat exchange fluid provided to the heatexchange region. The controller's microprocessor is capable of receivingthe signal representing the temperature of the patient and responding bycontrolling the heat exchange catheter to increase, decrease or maintainthe temperature of the patient within precise parameters as input by theuser.

A heat exchange device may also be supplied as a kit comprising the heatexchange device and a set of instruction for using the heat exchangedevice. The heat exchange device may comprise, for example, a heatexchange catheter as described in this application. The instructions foruse will generally instruct the user to insert the heat exchange deviceinto a body fluid containing region and to establish the temperature ofthe heat exchange device to affect the temperature of the body fluid.The instructions for use may direct the user to heat or cool the bodyfluid to achieve any of the purposes described in this application.

While all aspects of the present invention have been described withreference to the aforementioned applications, this description ofvarious embodiments and methods shall not be construed in a limitingsense. The aforementioned is presented for purposes of illustration anddescription. It shall be understood that all aspects of the inventionare not limited to the specific depictions, configurations or relativeproportions set forth herein which depend upon a variety of conditionsand variables. The specification is not intended to be exhaustive or tolimit the invention to the precise forms disclosed herein. Variousmodifications and insubstantial changes in form and detail of theparticular embodiments of the disclosed invention, as well as othervariations of the invention, will be apparent to a person skilled in theart upon reference to the present disclosure. It is thereforecontemplated that the appended claims shall cover any such modificationsor variations of the described embodiments as falling within the truespirit and scope of the invention.

What is claimed is:
 1. A method for controlling the temperature of atleast a portion of the body of a human or animal subject, said methodcomprising the steps of: A) obtaining a heat exchange catheter systethat comprises a heat exchange catheter and a controller, wherein: theheat exchange catheter comprises an elongate, flexible catheter havingan inflow lumen and an outflow lumen and at least one heat exchangerhaving first and second ends, the inflow lumen of the catheter beingconnected to the first end of the heat exchanger and the outflow lumenbeing connected to second end of the heat exchanger such that heatexchange fluid may be circulated into the first end of the heatexchanger, through the heat exchanger and out of the second end of theheat exchanger; and the controller receives i) a target temperatureinput and ii) a sensed subject body temperature input and causes heatedor cooled fluid to circulate into the first end of the heat exchanger,through the heat exchanger and out of the second end of the heatexchanger, to warm or cool the sensed subject body temperature as neededto cause the sensed subject body temperature to be approximately thesame as the target temperature; B) inserting the heat exchange catheterinto the vasculature of the patent and positioning the heat exchangerwithin a blood vessel through which blood is flowing such that theheated or cooled fluid will circulate through the heat exchanger in adirection opposite the direction in which blood flows through the bloodvessel; C) causing a temperature sensor to sense the temperature of atleast a portion of the subject's body and to communicate a sensedsubject body temperature input to the controller; D) inputting a targettemperature to the controller; and E) allowing the controller tocirculate heated or cooled fluid through the heat exchanger in adirection opposite the direction in which blood flows through the bloodvessel to thereby warm or cool the sensed subject body temperature asneeded to cause the sensed subject body temperature to be approximatelythe same as the target temperature;
 2. A method according to claim 1wherein the controller is adapted to receive sensed subject bodytemperature inputs from first and second temperature sensors and whereinStep C comprises causing first and second temperature sensors to sensethe temperature of at least a portion of the subject's body and tocommunicate first and second sensed subject body temperature inputs tothe controller.
 3. A method according to claim 1 wherein the temperaturesensor is selected from the group consisting of: tympanic temperatureprobes, esophageal probes, rectal probes, temperature probes formeasuring the temperature of the patient's blood, myocardial temperatureprobes, probes that measure core body temperature and skin temperatureprobes.
 4. A method according to claim 1 wherein the heat exchanger hasa diameter of 9 French or less, at least during insertion in Step B. 5.A method according to claim 1 wherein the heat exchange catheter furthercomprises imageable markers useable to ascertain the location of theheat exchanger within the subject's body and wherein the method furthercomprises the step of: imaging the imageable markers to ascertain thelocation of the heat exchanger within the subject's body.
 6. A methodaccording to claim 1 wherein the target temperature is belownormothermia and the method is carried out to cause the sensed subjectbody temperature to be hypothermic.
 7. A method according to claim 1wherein the subject is initially hyperthermic and the method is carriedout to cause the sensed subject body temperature to be approximatelynormothermic.
 8. A method according to claim 1 wherein the subject isinitially hypothermic and the method is carried out to cause the sensedsubject body temperature to be approximately normothermic.
 9. A methodaccording to claim 1 wherein the heat exchanger has an outer surfacewherein blood flow channels are formed.
 10. A method according to claim9 wherein helical blood flow channels are formed in the outer surface ofthe heat exchanger.